Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$187.34	12.174%	$210.1468	$210.15	$210.15	$210.10
Purchase #2	$77.70	7.111%	$83.2252	$83.23	$83.25	$83.20
Purchase #3	$94.67	11.349%	$105.4141	$105.41	$105.40	$105.40
Purchase #4	$7.61	7.746%	$8.1995	$8.20	$8.20	$8.20
Purchase #5	$115.84	6.818%	$123.738	$123.74	$123.75	$123.70
Purchase #6	$39.55	8.347%	$42.8512	$42.85	$42.85	$42.90
Purchase #7	$131.88	8.115%	$142.5821	$142.58	$142.60	$142.60
7 purchase totals =	$654.59		$716.1569	$716.16	$716.20	$716.10